The present application deals with a process for producing improved aqueous solutions of sodium hydrosulfide from readily available sources and suitable for many uses in industry. Trade requirements for useful sodium hydrosulfide solutions require that they be relatively concentrated and, although sodium carbonate is present in the sulfate paper process pulp treating solutions, it is desirable that sodium hydrosulfide solutions be substantially free of sodium carbonate for economic and solubility reasons.
In many cases, solutions of sodium hydrosulfide and other sodium compounds are prepared from refinery waste streams, including waste caustic streams and sour gas streams generated by refining processes. In particular, refinery sour gas streams are an economical source of hydrogen sulfide which can be converted into sodium hydrosulfide solutions of value in the sulfate paper and other industries. However, such refinery sour gas streams generally contain in addition to gaseous hydrocarbons and hydrogen sulfide a considerable carbon dioxide content as well as other impurities. In order to make these streams useful as sources of sodium hydrosulfide either a solution containing a considerable carbonate content must be accepted, though not desired, or methods for selective absorption of hydrogen sulfide must be developed.